Adaptive position/force control of robot manipulators with force estimation

In this paper, we design an adaptive position/force controller for robot manipulators during constrained motion. The proposed controller can compensate for parametric uncertainties while only requiring the measurements of the position and velocity of robot arms, but not the measurements of forces at contact points. A disturbance observer is designed to estimate the constraint forces. The control method results in semiglobal asymptotic tracking performance for the joint position and bounded tracking performance for the interaction force, also the controller provides proper estimate of constraint forces. It is shown mathematically that the error of tracking desired constraint force can be decreased sufficiently by increasing the control gains. The effectiveness of the proposed method is investigated through the numerical simulation for a two-degrees-of-freedom robot manipulator acting on a horizontal worktable.